Solvents are added to oil paints for temporary change, they are designed to work in a way such that they evaporate consistently and completely as the oil paint dries. (Technically, the more correct term is diluents, as not all are solvents, but it’s not the term very commonly used.) Solvents are also used to soften resins, making mediums, cleaning up, and also for cleaning brushes. It is very essential to use solvents in a well-ventilated room and you need to remember that they are flammable (catch fire easily).

Turpentine is the traditional solvent used in the oil painting. It’s actually based on tree resin and has a very fast evaporation rate, releasing harmful vapors. It could also be absorbed through healthy skin. Try using only artist quality turpentine as the industrial variety you will find in hardware stores probably contains impurities; it needs to be colorless, like water. It is also known as spirit of turpentine, oil of turpentine, genuine turpentine, English turpentine, distilled turpentine; double rectified turpentine, or even simply turps.